The instant invention is directed to a novel process for preparing silyl carbamates and novel silyl carbamates produced therefrom. More particularly, the instant invention is directed to a reaction between silyl hydrides and carbamates.
The preparation of silyl carbamates is generally accomplished by the insertion of carbon dioxide into the silicon-nitrogen bond of a silylamine. Although this insertion reaction was extensively studied in the sixties (Lappert and Prokai, Adv. Organometal, Chem., 5 (1967) 225,) the route has had limited attention and application because silylamines are frequently inconvenient and cumbersome to prepare. Other methods of limited appeal have been described in Cragg and Lappert, J. Chem. Soc. (A), (1966) 82; Berkofer and Sommer, J. Organometal Chem., 35 (1972) C15; and the literature set forth below. Accordingly, there exists the need for a more direct and facile method for preparing silyl carbamates.
Silyl carbamates themselves are well known in the art as reactive intermediates to a variety of useful products. In 1975 the reaction N,O-bis-(trimethylsilyl)carbamate with alcohols, phenols and carboxylic acids was reported to lead to the formation of trimethylalkoxy (and acetoxy) silanes, (L. Berkofer and P. Sommer, J. Organometal Chem., 99 (1975) C1). Mironov's group studied o-silylurethanes in some detail during the seventies. These workers noted that "all O-silylurethanes are readily hydrolyzed air, with the exception of PhNHCO.sub.2 SiMe.sub.3 which is surprisingly stable in air" (V. O. Sheludyakov, A. D. Kirilin, A. I. Gusev, V. A. Sharapov and V. F. Mironov, Zh, Obshch. Khim., 46 (1976) 2712). Methanol reacts with O-(trimethylsilyl) carbamates leading to the formation of trimethylmethoxysilane, carbon dioxide and an amine (M. E. Jung and M. A. Lyster, J. Chem. Soc., Chem. Comm. (1978) 315 and references therein). While the literature thus far cited is related to a few of the products which this invention can prepare, none of the work cited in the literature used the interaction of a silyl hydrogen and a carbamate to affect the synthesis of the silyl carbamate. Furthermore, there is no teaching of the preparation of alkoxysilylcarbamates and dicarbamates.